Yedikule Fortress (Turkish: Yedikule Hisarı or Yedikule Zindanları; meaning "Fortress/Dungeons of the Seven Towers") is located in the Yedikule neighbourhood of Fatih, Istanbul, Turkey. It was built in 1458 by adding three new towers to a section of the Walls of Constantinople which included the Golden Gate (Turkish: Altınkapı).
After his conquest of Constantinople in 1453, Ottoman Sultan Mehmed II had a new fort built in 1458. By adding three larger towers to the four pre-existing ones (towers 8 to 11) on the inner Theodosian wall, he formed the Fortress of the Seven Towers.
The Golden Gate lost its function as a gate, and for much of the Ottoman era, it was used as a treasury, archive, and state prison. Among others, the ambassadors of states currently at war with the Porte were usually imprisoned there. Among its most notable prisoners was the young Sultan Osman II, who was imprisoned and executed there by the Janissaries in 1622. The last Emperor of Trebizond, David Megas Komnenos, Constantin Brâncoveanu of Wallachia with his family, King Simon I of Georgia, and a number of leading Ottoman pashas were also among those executed there.